Chapter 4 Theory of Operation
Revision W HF Series X-ray Generators - Service Manual
4-6 Quantum Medical Imaging
Generator/OCP Communication
Communication with the Operator Control Panel Circuit is established via a 9-
pin connector and cable connected between the OCP and generator cabinet.
The 9-pin cable provides RS-485 serial communication, Operator Control
Panel Circuit hardware control lines and power supply lines. There are two
RS-232 service connections for connection to a personal computer for diag-
nostics, and for future interfacing with other systems.
Master and Slave Microcontroller Operation
Microcontroller U9 is the master microcontroller that controls the main func-
tions of the generator, based on states and settings set at the Operator Con-
trol Panel. Microcontroller U9 has it own internal ROM and RAM. It is driven
by a crystal oscillator at a clock speed of 32 MHz. Microcontroller U14 is con-
figured as a slave microcontroller that controls the auxiliary functions of the
generator, based on states and settings set by the master Microcontroller U9.
Microcontroller U14 has it own internal ROM and RAM. It is driven by a crystal
oscillator at a clock speed of 32 MHz.
There is a communication link between the master and slave for data and
status exchange. The Reset Circuit U8 monitors the +5 VDC supply voltage;
when it falls below +4.5 VDC, Microcontrollers U9 and U14 enter a reset
state. When the +5 VDC supply voltage returns to a level above +4.5 VDC,
the microcontrollers restart.
The master Microcontroller U9 has external Flash memory. The EPROM holds
part of the main program. The EPROM is accessed by U9 through the DATA/
ADDRESS bus of Microcontroller U9, with required Control Signals. On the
first clock cycle, the Flash memory address is stored in Latches U12 and U13.
On the second clock cycle, Microcontroller U9 reads data from Flash memory.
Microcontroller U9 communicates with the KVP & Filament Control Circuit to
set the digital-to-analog (D-A) converters and to read analog signals from
analog-to-digital (A-D) converters.
In addition, there are hardware signals that control the Filament Regulator
Control Circuit and KVP & Filament Control Circuit. Some of the key signals
are isolated using opto-couplers. On systems utilizing the AEC option, the
same connector (J1) is connected to the AEC board in parallel.
The interface board controls all external signals needed to interface to the
tube stand, wall stand, and table. Some of the signals coming are isolated by
opto-couplers. J2 interfaces to the line monitor board. The line monitor board
supplies the 24VDC for the brakes. The line monitor supplies a sample of the
400 VDC bus for monitoring by Microcontroller U14, which uses an internal A-
D converter to monitor key voltages including the +5V, 15V, 24V, 24V brake
supply voltages. U16 is the 4.8V voltage reference for Microcontroller U14
internal A-D. Microcontroller U14 controls the Rotor Board; it provides the
necessary signals for boost and run, and it monitors the tube rotation signal
and rotor temperature.
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